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首页> 外文期刊>IEEE Transactions on Information Theory >Two-Way Networks: When Adaptation is Useless
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Two-Way Networks: When Adaptation is Useless

机译：双向网络：当适应无用时

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Most wireless communication networks are two-way, where nodes act as both sources and destinations of messages. This allows for adaptation at or interaction between the nodes—a node's channel inputs may be functions of its message(s) and previously received signals allowing for potentially larger rates than those achievable in feedback-free one-way channels where inputs are functions of messages only. However, examples exist of channels where adaptation is not beneficial from a capacity perspective. We ask whether analogous results hold for several multiuser two-way networks. We first consider deterministic two-way channel models: the binary modulo-2 addition channel and a generalization of this, and the linear deterministic channel, which models Gaussian channels at high SNR. For these deterministic models, we obtain the capacity region for the two-way multiple access/broadcast channel (MAC/BC), the two-way Z channel, and the two-way interference channel (under certain partial adaptation constraints in some regimes). We permit all nodes to adapt their channel inputs to past outputs (except for portions of the linear high-SNR two-way interference channel where we only permit two of the four nodes to fully adapt). However, we show that the two-way fully or partially adaptive capacity region consists of two parallel one-way regions operating simultaneously in opposite directions, i.e., adaptation is useless. We next consider two noisy channel models: 1) the Gaussian two-way MAC/BC, where we show that adaptation can at most increase the sum-rate by (1/2) bit in each direction and 2) the two-way interference channel, where partial adaptation is shown to be useless when the interference is very strong. In the strong and weak interference regimes, we show that the nonadaptive Han and Kobayashi scheme utilized in parallel in both directions achieves to within a constant gap for the symmetric rate of the fully (for some regimes) or partially (for the remaining reg- mes) adaptive models. The central technical contribution is the derivation of new, computable outer bounds which allow for adaptation.
机译：大多数无线通信网络都是双向的，其中节点既充当消息的源，又充当消息的目的地。这允许在节点之间进行自适应或在节点之间进行交互-节点的通道输入可能是其消息和先前接收到的信号的函数，从而可能比无反馈单向通道（其中输入是消息的函数）所能达到的速率更高只要。但是，从容量的角度来看，存在一些渠道的例子，其中适应对受益无益。我们问类似的结果是否适用于几个多用户双向网络。我们首先考虑确定性的双向通道模型：二进制模2加法通道及其推广，以及线性确定性通道，该通道以高SNR建模高斯通道。对于这些确定性模型，我们获得了双向多路访问/广播信道（MAC / BC），双向Z信道和双向干扰信道的容量区域（在某些情况下在某些部分自适应约束下） 。我们允许所有节点将其通道输入调整为过去的输出（线性高SNR双向干扰通道的部分除外，在该部分中，我们仅允许四个节点中的两个完全适应）。但是，我们表明，双向完全或部分自适应容量区域由两个在相反方向上同时运行的平行单向区域组成，即自适应是无用的。接下来，我们考虑两个有噪声的信道模型：1）高斯双向MAC / BC，其中我们展示了自适应最多可将每个方向上的总速率增加（1/2）位，以及2）双向干扰信道，当干扰非常强时，表明部分适应是无用的。在强干扰和弱干扰两种情况下，我们表明在两个方向上并行使用的非自适应Han和Kobayashi方案在完全（对于某些方案）或部分（对于其余方案）的对称速率上均达到恒定的差距。 ）自适应模型。核心的技术贡献是派生出了新的，可计算的，允许适应的外部边界。

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